This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: asm issues
- To: Robert Kennedy <rkennedy at cthulhu dot engr dot sgi dot com>
- Subject: Re: asm issues
- From: Jeffrey A Law <law at upchuck dot cygnus dot com>
- Date: Fri, 07 May 1999 00:14:26 -0600
- cc: rth at cygnus dot com, torvalds at transmeta dot com, egcs at egcs dot cygnus dot com
- Reply-To: law at cygnus dot com
> Actually I see now that my remarks, too, underrated decent points-to
> analysis. There is no particular reason why (*foo) can't be kept in a
> register by an intelligent enough compiler, and I know for a fact that
> there are compilers that routinely do it.
gcc is among those compilers. Though it's support for this kind of thing
isn't as aggressive as other compilers. Expect that to be changing :-)
> To summarize: I don't (think I) like volatile as a means of forcing no
> copy-in/copy-out because I don't yet see a complete correspondence
> between that usage and the semantics of volatile in other
> circumstances. I also don't like using anything in the constraints to
> specify whether copy-in/copy-out is allowed.
We don't have a lot of ways to pass this kind of information to an asm....
Seems to me you have to use one or the other. This is kind of what we've
used volatile for for years...
jeff